The present invention relates to an adjusting device for pivoting a pivotal element of the piece of furniture. The piece of furniture is used in living and working areas of a home or in a sanatorium or health spa.
Such adjusting devices are utilized on beds whose headrest and/or leg part is adjustable in height for example for the purpose of meeting the individual ideas of the user. Its utilization on armchairs, cupboards or other pieces of furniture is conceivable as well.
In the adjusting devices disclosed for example in the German Patents DE 44 33 934 A1 or DE 42 11 352 C2 or in the German published application DE-OS 23 26 709, a spindle is attached to a lever arm which is accommodated on a torsion bar in order raise the headrest or the leg part by way of said torsion bar. The torsion bar is thereby arranged in the axis of rotation of the headrest or leg part. The torsion bars to be used have to be capable of transmitting the high rotation and torsion moments of more than 500 nm that occur thereby and are to be designed accordingly and preferably be made from metal. Such a device requires expensive fittings and is difficult to retrofit on already existing beds.
The German Utility Model DE-G 93 07 322.4 describes a retrofittable, motor driven lifting apparatus for moving headrest and/or leg parts of a supporting framework of a bed in which a cross-beam that holds a driving motor and a scissor-type rod assembly is placed onto the frame of the supporting framework. The upper, free side of the scissor-type rod assembly is guided in a guide beam and is fastened to the headrest or leg part of the supporting framework. The scissor-type rod assembly and, as a result thereof, the headrest or leg part, are moved through a spindle that connects the two shear elements and through an actuating drive that displaces the spindle in axial direction. The arrangement of the spindle effects that, on account of the dead weight of the headrest or leg part, or of the person resting thereon, said spindle is mainly loaded in tension. In contrast to the previously described prior art, the lifting apparatus according to the German Utility Model DE-G 93 07 322.4 substantially transmits tensile and pressure loads onto the supporting framework and onto the proper headrest part, whereas the bending moments transmitted are negligible and may be absorbed by the existing supporting framework or headrest part without the need for reinforcing the same by means of expensive fittings.
The lifting apparatus according to the German Utility Model DE-G 93 07 322.4 consists of many complicated individual pieces that moreover are to be manufactured with large dimensions in order to be capable of diverting the loads. Furthermore, the scissor-type rod assembly involves the risk that objects or body parts such as arms or legs get caught therein in the process of traveling the headrest or leg part, thus causing damage or even injury.
In view thereof it is the object of the present invention to provide an adjusting device that may be easily mounted to any type of mattress frames without having to install expensive fittings and that minimizes the risk of injury.
The technical solution in accordance with the present invention consists in proposing an adjusting device having the features of claim 1. Advantageous developments of this adjusting device are to be found in the subordinate claims.
The adjusting device in accordance with the invention has the advantage that it only needs to be fastened to the piece of furniture at two or three points so that the adjusting device is almost cantilevered. Accordingly, both the pivotal and the retaining arm may be easily fastened to the piece of furniture without the help of fittings, this being the reason why the adjusting device may be utilized without great expenditure in the manufacture of supporting frameworks and why it is possible to retrofit already existing supporting frameworks at low cost.
Another advantage is that the risk of injury with the adjusting device according to the invention is very low since, in this case, there are merely two arms moving relative to one another and since the retaining arm and the actuating arm project from the cross-beam of the supporting framework into the inside of the piece of furniture, more specifically into a free space located underneath the supporting framework. As a result thereof, the adjusting device is hardly visible and accessible from the outside so that the adjusting device is protected against accidental damages as well.
Still another advantage is that the cost of production is low as there are few movable parts. As a result thereof, the dead weight could also be reduced, which permits to further save material and cost.
The advantage of having retaining arm and actuating arm arranged on one plane is that the space needed is kept small so that the adjusting device may also be mounted in small pieces of furniture or in pieces of furniture that have only little mounting space available.
In a preferred embodiment, the actuating drive is held on a retaining arm that is rigidly fastened to the piece of furniture, thus making certain of simple installation and low-cost manufacture.
On a retaining arm which is rigidly mounted on the fixed element, the free end of the actuating arm moves on an orbit that needs not be identical to the orbit of the headrest part. To compensate this difference, the actuating arm is advantageously held on the pivotal element, or on the headrest part respectively, by means of a length compensating device. This length compensating device may be a long hole for example.
In a preferred embodiment, this length compensating device is dispensed with, the retaining arm being also pivotally arranged on the fixed element instead. As the retaining arm is now pivotal as well, the actuating arm is capable of moving the entire adjusting device up- or downward within certain limits when it is moved upward for the purpose of compensating the differential orbits of actuating arm and headrest part. Concurrently, as a result thereof, the adjusting device only transmits tensile and pressure loads onto the supporting framework and the headrest part, and the rotation and torsion moments that wear the material are not occurring any longer. Accordingly, the forces emanating from the adjusting device in accordance with the invention may be absorbed and transmitted by commercially available supporting frameworks without the need for expensive or additional fittings or other material reinforcing pieces.
Still another advantage of the adjusting device is that, since the actuating arm is arranged across the main direction of movement, the adjusting device may be arranged simply and without any additional tools on the pivotal element, said adjusting device extending far into the inside of the piece of furniture, thus preventing the adjusting device from causing injury to the user or damage to the material.
As only few component parts are needed, the friction between the parts is reduced. Accordingly, a smaller driving motor may be chosen which in turn further lowers the cost.
Still another advantage is that the adjusting device in accordance with the invention may easily be retrofitted on already existing supporting frameworks, since merely the retaining arm needs to be arranged either rigidly or pivotally on the cross-beam of the supporting framework (of the fixed element) and since the actuating arm merely needs to be arranged pivotally on the cross-beam of the headrest part (pivotal element). As a result thereof, it is possible for an amateur mechanic to mount the adjusting device in accordance with the invention to already existing supporting frameworks.
In a particularly preferred embodiment, the actuating drive is pivotally held on the retaining arm or on the piece of furniture by way of a holding device. The advantage thereof is that the circular motion executed by the end of the actuating arm facing the spindle on being pivoted is retraced by the spindle and the entire actuating drive so that the normally occurring transverse loads which act on the actuating drive do not arise as a result thereof. On one side, this leads to a much smaller size of the individual component parts of the actuating drive and of the adjusting device, and accordingly, to reduction of cost and on the other to longer work life since the transverse loads that damage the device do not occur any longer.
In order to provide a reliable holding device that moreover permits a pivotal movement of the actuating drive, it proved advantageous to provide at least one jib with a spherical or cylindrical end that engages into a corresponding recess arranged on the actuating drive. Thanks to the spherical or cylindrical shape of the free jib end, said jib may be retained in the recess and still be pivoted.
In a preferred development, it proved advantageous to extend the recess radially away from the axis of the spindle. When more specifically two such recesses are arranged directly opposite one another, the actuating drive may easily be pivoted about the thus formed pivot axis while still being reliably retained.
In a preferred development, the recess surrounds more than 180 degrees of the spherical or cylindrical end of the jib. As a result thereof, the jib is positively fastened in the recess so that the actuating drive is prevented from accidentally slipping out.
In another advantageous embodiment there is provided a friction clutch between actuating arm and retaining arm. This constructional separation between actuating arm and retaining arm interrupts the flow of forces from the driving motor to the pivotal element. This signifies that, in the event an obstacle gets caught between headrest part and supporting frame when lowering for example the headrest part, the actuating drive continues to be moved, but the force that emanates from the driving motor is not transmitted to the obstacle as this is prevented from happening on account of the separation between actuating arm and retaining arm. The obstacle is thus prevented from being damaged and the operator from being injured.
The friction clutch advantageously comprises a catch carried on the spindle and serving to rotatably receive the actuating arm, the front side thereof, which is turned away from the housing, being undulated and being engageable with a buffer which is located at the end of the spindle and is also given a corresponding undulated shape. The advantage thereof is that the loaded actuating arm presses the undulated front side of the catch against that side of the buffer that is given the corresponding undulated shape so that, on account of this positive connection, the spindle is reliably prevented from rotating in unison therewith. The normally used locking to prevent twisting of the spindle is no longer necessary as a result thereof.
Furthermore, the present invention is based on the appreciation that the actuating drive of the adjusting device must absorb very large axial forces in order to be capable of adjusting the element to be adjusted, more specifically when a person is resting thereon, and that the radial forces occurring thereby are much smaller.
A particularly preferred embodiment is characterized by an actuating drive with a driving motor whose driven shaft is configured as a worm, with a spindle that is held in a worm wheel in such a manner that it is axially movable, the worm meshing with the worm wheel, and with a housing that carries the driving motor and rotatably accommodates the worm wheel, wherein, between worm wheel and housing, there is provided at least one needle bearing for absorbing the axial forces and at least one sliding bearing for absorbing the radial forces.
An actuating drive configured in accordance with this technical teaching has the advantage that the needle bearing can reliably absorb the high axial forces that occur without any damage and that the small forces may also be sufficiently absorbed by a low-cost sliding bearing. I.e., the present invention permits to substitute a less expensive needle bearing and an even less expensive sliding bearing for the expensive prior art ball bearing. Concurrently, as the needle and/or the sliding bearing require only little place, the housing may be given accordingly smaller dimensions, which contributes in saving costs.
In a preferred embodiment, two spaced apart sliding bearings are provided in the actuating drive. The advantage thereof is that, on pivoting the actuating arm, possibly occurring transverse loads may better be diverted on account of the favorable lifting conditions. Another advantage is that, thanks to the spacing of the two sliding bearings, the forces occurring on pivoting the actuating arm are transmitted onto the actuating drive through the sliding bearings and not through the very spindle. As a result thereof, the susceptible spindle and the susceptible worm wheel are less exposed, which leads to a longer work life.
The recesses for receiving a jib of a holding device that are arranged opposite one another on the housing in such a way that they extend radially from the axis of the spindle have the advantage that the actuating drive may be pivoted about the pivot axis formed by the recess as a result thereof, thus making certain of a reliable hold and a controlled pivotal movement.
In another preferred development, the recess surrounds more than 180 degrees of the spherical or cylindrical end of the jib, thus providing a positive connection between actuating drive and holding device out of which the actuating drive cannot be released without the use of force.